模板剂对SAPO-34分子筛性能的影响研究

Research of the Influence of Template on Properties of SAPO-34 Molecular Sieves

摘要:

采用XRD、SEM、NH3-TPD等方法深入研究了以三乙胺(TEA)、四乙基氢氧化铵(TEAOH)及二者的混合物为模板剂合成的产物的结构及物化性能。并以甲醇为探针分子，在固定床反应器上对合成产物在甲醇制取烯烃(MTO)反应中的催化性能进行了评价。结果表明，模板剂的种类及配比对所得产物的晶相结构、晶粒大小、酸强度、酸量以及催化性能有重要影响。双模板体系中，当TEAOH/ TEA=0.037～0.186时，可以得到纯SAPO-34分子筛；且当TEAOH/TEA=0.093时，得到的SAPO-34分子筛晶粒较小(1.0μm左右)且均匀，酸度适中，低碳烯烃(C2=～C4=)的选择性94.98%，催化寿命415min，较单独以TEA(TEA/Al2O3=2.15)或TEAOH(TEA/Al2O3=2.0)为模板剂合成的催化剂的低碳选择性 (88.22%和89.29%)和寿命(170min和165min)均有明显提高，且积炭速率(0.016%/min)明显降低。

Abstract:

The structure and property of products which were synthesized with TEA and/or TEAOH as template(s) have been studied deeply by XRD, SEM and NH3-TPD techniques, and the catalytic performance of products have been investigated in conversion of methnaol-to-olefine (MTO) fixed-bed process. The results from the XRD, SEM, NH3-TPD measurements showed that the types and ratios of the templates had a great influence on the structure, crystal size and acidity of the products. In the dual-template system, the pure SAPO-34 molecular sieves could be obtained as TEAOH/TEA=0.037-0.186, and the SAPO-34 molecular sieve with smaller and uniformer crystal, medium acidity could be obtained as TEAOH/TEA=0.093. The catalytic evaluation showed that the SAPO-34 synthesized with TEAOH/TEA=0.093 exhibited higher selectivity to light olefin (C2=-C4=) (94.98%), longer lifetime (415min) than the SAPO-34 prepared with the single TEA (TEA/Al2O3=2.15, 88.22%, 170min) or TEAOH (TEA/Al2O3=2.0, 89.29%, 165min) as template, and its coke deposition rate have fallen remarkly (0.016%/min).